Expression profile of microRNAs in bladder cancer and their application as biomarkers

Bladder cancer (BC) comprises 3% of all cancers and is particularly common in the developed countries. Early diagnosis is an important necessity in improvement of BC prognosis, as patients' outcome is significantly different between muscle invasive BC (MIBC) and non-muscle invasive BC cases. This cancer is resulted from an intricate interaction between genetic and environmental factors. Recent studies have identified microRNAs (miRNAs) as potential modulators of carcinogenic potential of BC cells. These small transcripts regulate expression of target genes mostly through binding with their 3' untranslated regions. Expression of several oncomiRs has been increased in BC tissues, peripheral blood or urine samples of these patients. These miRNAs promote oncogenic potential of BC through modulation of epithelial-mesenchymal transition or PI3K/AKT, JAK/STAT and NF-κB/Snail signaling pathways. Besides, a number of tumor suppressive miRNAs have been down-regulated in BC samples leading to enhanced proliferation, invasiveness and metastasis of these cells. TGFβ1, Akt, MAPK, MET/SMAD3/SNAIL, MAPK1/Slug/vimentin and Wnt7a/β-catenin pathways and axes are among molecular targets of these miRNAs. Aberrant expressions of miRNAs in biofluids of patients with BC have potentiated them as molecular markers for prediction of disease course. In the current review, we provided a summary of studies which reported aberrant expression of miRNAs and their implications in the diagnosis or prognosis of patients with BC.